P.M.R. spectra of heteroaromatic molecules containing bridgehead nitrogen atoms. II. 5-Methyl-s-triazolo[4,3-a]quinoline and s-Triazolo[4,3-a]quinoline

Abstract

A detailed analysis of the spectra of 5-methyl-s-triazolo[4,3-a]quinoline and s-triazolo[4,3-a]quinoline in CDCl₃ and (CD₃)₂SO solution was carried out. Measurements were made over a range of temperatures, and multiple-resonance experiments carried out as aids to the confirmation of assignments. The peaks in the spectrum corresponding to H8 were observed to show non-first-order effects, arising from long-range coupling to H4, which were dependent upon the temperature at which the spectrum was obtained. It was found that these effects arose from the variation in the relatively small chemical shift between H6 and H9 and furthermore that the experimental splitting pattern could be used to determine the relative signs of J_4,6 and J_4,8. Confirmation was obtained that these two coupling constants have the same relative sign.